Adding legend to ggplot when lines were added manually
ggplot2, r
Solution
Just set the color name in `aes` to whatever the line's name on the legend should be.
I don't have your data, but here's an example using `iris` a line with random y values:
library(ggplot2)
line.data <- data.frame(x=seq(0, 10, length.out=10), y=runif(10, 0, 10))
qplot(Sepal.Length, Petal.Length, color=Species, data=iris) +
geom_line(aes(x, y, color="My Line"), data=line.data)
The key thing to note is that you're creating an aesthetic mapping, but instead of mapping color to a column in a data frame, you're mapping it to a string you specify. `ggplot` will assign a color to that value, just as with values that come from a data frame. You could have produced the same plot as above by adding a `Species` column to the data frame:
line.data$Species <- "My Line"
qplot(Sepal.Length, Petal.Length, color=Species, data=iris) +
geom_line(aes(x, y), data=line.data)
Either way, if you don't like the color `ggplot2` assigns, then you can specify your own using `scale_color_manual`:
qplot(Sepal.Length, Petal.Length, color=Species, data=iris) +
geom_line(aes(x, y, color="My Line"), data=line.data) +
scale_color_manual(values=c("setosa"="blue4", "versicolor"="red4",
"virginica"="purple4", "My Line"="gray"))
Another alternative is to just directly label the lines, or to make the purpose of the lines obvious from the context. Really, the best option depends on your specific circumstances.
Problem
I have a plot in ggplot with 4 separate lines that I have added with a separate geom_line() argument. I would like to add legend but scale_colour_manual doesn't work in this case. What is the proper way to add legends when I added the variables separately? Here's my code: ``` ggplot(proba[108:140,], aes(c,four)) + geom_line(linetype=1, size=0.3) + scale_x_continuous(breaks=seq(110,140,5)) + theme_bw() + theme(axis.line = element_line(colour = "black", size=0.25), panel.grid.major = element_blank(), panel.grid.minor = element_blank(), panel.border = element_blank(), panel.background = element_blank()) + theme(axis.text.x = element_text(angle = 0, hjust = +0.5, size=6,color="black")) + theme(axis.text.y = element_text(angle = 0, hjust = -100, size=6, color="black")) + theme(axis.ticks=element_line(colour="black",size=0.25)) + xlab("\nTime-steps") + ylab("Proportion correct\n") + theme(axis.text=element_text(size=8),axis.title=element_text(size=8)) + geom_line(aes(c,three), size=0.2, linetype=2) + geom_line(aes(c,one),linetype=3, size=0.8, colour="darkgrey") + geom_line(aes(c,two), linetype=1, size=0.8, colour="darkgrey") ```